It's happened to all of us: we forget where we parked our car or why we walked into a room. Some amount of forgetfulness is normal, especially when you're busy or have a lot on your mind. But for nearly five million Americans, that forgetfulness will progress into Alzheimer's disease. Decades of research have shown that the buildup in the brain of toxic proteins, called beta amyloid and tau, can lead to Alzheimer's. What's less clear is what causes these proteins to accumulate. Some new studies have begun to explain this process, revealing that the causes of Alzheimer's disease go beyond genetics and unhealthy habits (though those are important factors, too). Here, some of the most unusual (and scary!) causes new science is pointing to. (Boost your memory and age-proof your mind with these natural solutions.)

You're on anti-anxiety meds.
A class of medications called benzodiazepines, which include the popular drugs lorazepam (Ativan), alprazolam (Xanax), and clonazepam (Klonopin), are frequently used to treat anxiety and insomnia. Although studies evaluating the safety and efficacy of these drugs have only evaluated their short term use (generally three months or so), many people take them long-term. A study published in the British Medical Journal followed 1,796 Canadians with Alzheimer's disease and 7,184 healthy controls for six years and found that taking benzodiazepines for more than three months was associated with up to a 51% increase in Alzheimer's disease.

The moral of the story? If you need benzodiazepines only on occasion, you're probably safe. If anxiety and insomnia are a regular issue for you, consider cognitive behavioral therapy, which has been found to effectively treat both conditions—without the harmful side effects of drugs.

You've hit your head one too many times.
With an estimated 300,000 Americans getting a sports-related concussion each year, according to data from the University of Pittsburgh's Brain and Spine Injury Program, lots of us are familiar with the worries that can accompany a head injury. Most people recover without a hitch, but for others, the inflammation that helps to heal the damaged brain tissue becomes chronic. Here is where the potential links to Alzheimer's disease can be found, says Brian Giunta, MD, PhD, a psychiatrist and neuroscientist at the University of Southern Florida.

Cells in your brain called microglia play an important role in inflammation. "When the microglia are constantly in a pro-inflammatory state, they are less able to clear amyloid beta from the brain," Giunta says.

Without microglia to clear the misfolded proteins, it can build up in the brain and kill neurons. It's still not clear why the inflammatory process stays switched on in some people or how many cases of Alzheimer's disease are potentially linked with traumatic brain injury, Giunta says.

You're regularly sleep-deprived.

A lack of sleep has hit near-epidemic levels in recent years, as we attempt to juggle career, children, marriages, hobbies, and more. For lots of us, something's gotta give—and many of us choose to sacrifice shut-eye. Besides making you drowsy behind the wheel and giving you the midnight munchies, this sleep loss can also speed up the development of Alzheimer's disease, according to a study published in the Neurobiology of Aging.

"Sleep problems are common in people with Alzheimer's disease, but it wasn't clear whether this was cause or effect," says Domenico Praticò, MD, a pharmacologist and immunologist at Temple University in Philadelphia. In a mouse model of Alzheimer's disease, Praticò and colleagues found that letting these mice only sleep for four hours a night increased the amount of tau in their brains. It also altered learning and memory, as well as how well neurons were able to communicate with each other. Chronic sleep deprivation, Praticò explains, stresses the brain and body (which is why you may be so tired), which speeds up the harmful processes leading to Alzheimer's disease.

"Sleep deprivation is a form of chronic stress on the body. It's also the time when the brain gets rid of bad things," such as excess amyloid beta protein, Praticò said. (Stop stressing your body with these tips to sleep better.)

You're lonely.

Remaining engaged with friends and the broader community is part of what many of us consider the good life. It's good medicine, too. A study in the Journal of Neurology, Neurosurgery, and Psychiatry identified links between loneliness and the development of dementia. The researchers found that feelings of loneliness in older adults gave them 1.63 times the odds of developing dementia during the three years of the study. Scientists still don't know what's driving this association, but the implications are clear: Staying connected is good for you.

You have diabetes in your brain.
To neuroscientist Suzanne de la Monte, MD, of Brown University, Alzheimer's disease is really a metabolic disease that affects the brain. The links are so close that she has begun referring to Alzheimer's disease as Type 3 diabetes.

Brain cells use glucose as fuel, and insulin tells these cells to slurp up glucose in the blood. De la Monte's big insight was that brain cells can develop insulin resistance, just like other cells in the body.

"Any organ can be affected by insulin resistance," de la Monte says. "You can have it in the liver- we call that non-alcoholic fatty liver disease. If you get it in the kidney, we call it renal disease. If you get it in the brain, we call it Alzheimer's."

Her research over the past few years has revealed that this creates a toxic environment for the brain, leading to the harmful buildup of proteins and neuron death seen in Alzheimer's.

In addition to telling us more about how Alzheimer's can be prevented through healthy diet and exercise, it could also help potentially treat the disease. Preliminary studies have shown that inhaled insulin can help reduce symptoms of Alzheimer's dementia.